In many countries across the world, it is considered rude for a guest not to take off their shoes before entering a private home. A U.S. expert now says that it may not be beneficial.

Stephen S. Morse, a professor of epidemiology at the Mailman School of Public Health at Columbia University says that even when a person walks through a spotless office building, shoes pick up all sorts of germs and bacteria.

Bacteria like E. coli and viruses that cause influenza like to attach themselves to shoes. For those who live in farmland or near exposed soil, harmful pathogens like to stick on shoes. Carpets and wet surfaces house our favorite fungi, which can cause Athlete's foot and plantar warts.

However, these germs would "have to make their way into a human through a lesion on the skin, and that's a pretty far-fetched scenario," Morse told the Wall Street Journal.

While the risk of catching any severe germs is low, who should enforce a no-shoes policy?

Those who have crawling babies should enforce a no-shoe rule, as babies love to put anything they can find in their mouths, or leave things behind for an adult to step on. Dr. Morse also offers this practical reason: wood floors and other surfaces look cleaner without shoe traffic. Dr. Morse removes his shoes in his home, "for the sake of keeping my marriage intact."

However, going barefoot is not for everyone. Diabetics and the injury-prone should either wear shoes in the house or socks and slippers. "You could step on a nail," Dr. Morse says. "But mostly the concerns are anesthetic."

Enforcing the no-shoe rule can be tricky, especially when it comes to repairmen or dinner guests, and Dr. Morse doesn't believe it's worth it. He thinks that a little dirt is a good thing: "The Hygiene Hypothesis says that one of the reasons we see asthma and allergies is because the immune system isn't being kept busy with fighting off the bad guys," he says. "There is evidence for both sides, and we epidemiologists debate this every week."

As long as guests wipe off their shoes before they enter your home, you should be OK. "It might save your floors a lot of cleaning, but other than that, we have no reason to believe that shoes in the home are a real hazard."